Fixture

ABSTRACT

A fixture for connecting two or more elongate bars in end to end relationship. The bars are provided with ribs on an external surface thereof. The fixture comprises a set of inner segments with formations to engage with the ribs on the bars. A set of intermediate segments and/or an outer sleeve is then positionable around the inner segments to maintain the same in position. The outer sleeve passes over the intermediate segments and mechanically engages the segments and members in the end to end relationship.

[0001] The invention to which this application relates is a fixture inthe form of a mechanical connection device and particularly, but notexclusively, to a fixture for joining concrete reinforcing steel bars,for joining any other surface profiled bars or creating an anchor on asingle profiled bar.

[0002] Concrete reinforcing steel bats are used, as the name suggestsfor reinforcing concrete structures. The bars can be provided indifferent sizes and have different forms of rib patterns on their outersurfaces, to provide a mechanical interface between the bar and theconcrete which surrounds the bar in use. The steel bars typically haveto be mechanically connected together in forming the structure butconventional methods can compromise the fatigue performance and strengthof the bars, which in turn, compromises the integrity of the finalstructure.

[0003] The technical requirements of the reinforcing bars generallyrelate to providing optimal tensile/compressive capability, strainperformance and fatigue life. Conventionally, specialised equipment isemployed to achieve these requirements, either at the point ofinstallation or at a location where an additional process his to becarried out. One such example of a connector for connecting two barstogether and requiring additional machinery is disclosed in U.S. Pat.No. 5,967,691. The ends of the bars in this connector assembly arerequired to have different outer surface formations to the remaindersurface of the bars, thereby allowing shell elements to placed aroundthe bar ends to bridge and connect the bars together. These outersurface formations are required to be machined or welded on. However,deformation of the bar is likely to compromise the fatigue performanceof the bar. In addition, the requirement of additional equipment incursexpense through additional handling and the expense of the equipmentitself. Furthermore, transport of equipment to the location ofconstruction is often problematic, particularly in less developedcountries where transport systems are more primitive. There is also theadditional problem in that the skill level required to correctly carryout these specialised operations is not always readily available at thesite where the process is to be carried out.

[0004] A further type of connector assembly is disclosed in GB2255385,wherein the assembly comprises a set of wedge shaped claws for locationat each end of the bars being connected. Two externally threaded innerbushings are located over the claws and are joined to an internallythreaded outer bushing, Problems associated with this type of connectorare that some of the components require to be screwed together duringassembly. As the bars are typically heavy and embedded in concrete, theyare often not capable of being rotated. In addition, embedding of theassembly components onto the bars and with each other typically does notoccur until application of the service load of the structure (load ofthe assembled structure on the bars in use). As a result, slipping ofthe components occurs on application of the service load, therebyresulting in cracking and/or damage to the structure.

[0005] It is therefore an aim of the present invention to provide afixture in the form of a mechanical connection device for connectingtogether lengths of profiled material, such as concrete reinforcingsteel (rebar), the fixture overcoming the abovementioned problems andbeing capable of use with material of different sizes and differentouter surface profiles.

[0006] It is a further aim of the present invention to provide a fixturewhich can be used in accordance with the relevant internationalrequirements, such as tensile/compressive capability, strain performanceand fatigue life, without the need for any specialised equipment and bythe most cost-effective means.

[0007] According to a first aspect of the present invention there isprovided a fixture for connecting two or more concrete reinforcingmembers together in end to end relationship, said two or more membershaving outer profiled surfaces, said fixture including sets of innersegments, intermediate segments and an outer sleeve and characterised inthat each set of inner segments have formations co engage with the outerprofiled surfaces of each end of the members being connected, said innersegment formations being of complementary dimensions to the outerprofiled surfaces of the members for location therewith, theintermediate segments having formations on an inner surface thereofcomplementary to formations on the outer surface of the inner segmentsto provide mechanical interlock therebetween, and an outer sleevepositionable around the sets of inner segments and intermediate segmentsto maintain the same in position.

[0008] Preferably the set of inner segments include a pair of segmentsfor location around each of the two members, being of sufficient lengthto generate sufficient rib shear area.

[0009] Further preferably the set of intermediate segments includes apair of segments for location around said inner segments and said two ormore members.

[0010] Preferably the inner segments have the formations on an innersurface, and are of complementary dimensions to the profiled surface ofthe members. The inner segments can also be provided with a profiledouter surface fur engagement with complementary formations on the innersurface of the intermediate segments and these surfaces typicallyinclude fine pitch thread.

[0011] Preferably a semi-compressible fluid or coating is providedbetween the members and the inner segments to reduce clearancetherebetween. In one embodiment this fluid is an extrudable coating. Thecoating intimately interfaces with the members to be joined in order toavoid any slip, and transfer any load within the members to their matingcomponents.

[0012] In one embodiment the two or more members arc elongate barsprovided with a plurality of ribs on their outer surfaces.

[0013] Preferably the inner segments can be held in place by securingmeans in the form of a spring clip, rubber band, tying wise and/or thelike, which is located in a recess portion on the outer surface of thesegments.

[0014] In a further embodiment of the present invention an outer sleeveis provided for locating around the intermediate segments to maintainthe components in position. Preferably in this embodiment theintermediate segment is tapered and the outer sleeve has a complementarytaper to provide a frictional fit between the same The taper istypically between 0-3 degrees.

[0015] In an alternative embodiment no outer sleeve is provided and theintermediate segments are the outermost component of the assembly. Inthis embodiment fastening means are provided on the intermediatesegments to secure the assembly together. Preferably these fasteningmeans are recessed or flush with the outer surface of the intermediatesegments.

[0016] Typically, the internally coned outer sleeve is driven over theintermediate segments by manual force such as by a hammer and generatesa radial compressive force. This force embeds the inner segments ontothe members and into the intermediate segments taking up any clearancescaused by manufacturing tolerances of all components thereby minimisingslip.

[0017] In a preferred embodiment the outer sleeve has an indicationdevice, which will inform the installer when sufficient hammer blowshave been applied.

[0018] The mechanical splice in accordance with the invention meets theneeds of the commercial market, and has the following design features:

[0019] An intimate mechanical interlock with each of the members to bejoined which has sufficient cross-sectional area in axial shear to beable to withstand the full tensile/compressive strength of the memberswithout movement or slip, including the situation where load reversaloccurs.

[0020] A large enough cross-sectional area at the location of thehighest tensile stress to be able to withstand the full tensilecapability of the members.

[0021] The mechanical connector does not adversely compromise thefatigue performance of the members.

[0022] In a second aspect of the present invention there is provided afixture for connecting at least one concrete reinforcing member to anobject, said at least one member having outer profiled surfaces, saidfixture including sets of inner segments, intermediate segments and anouter sleeve and chatacterised in that each set of inner segments haveformations to engage with the outer profiled surfaces of each end of themembers being connected, said inner segment formations being ofcomplementary dimensions to the outer profiled surfaces of the membersfor location therewith, the intermediate segments having formations onan inner surface thereof complementary to formations on the outersurface of the inner segments to provide mechanical interlocktherebetween, and an outer sleeve positionable around the sets of innersegments and intermediate segments to maintain the same in position.

[0023] In a further aspect of the invention there is provided a fixturefor connecting two or more elongate concrete reinforcing members in endto end relationship, said members provided with ribs on an externalsurface thereof, said fixture including sets of inner segments,intermediate segments and an outer sleeve and characterised in that eachset of inner segments have formations to engage with the ribs at eachend of the members being connected, said inner segment formations beingof complementary dimensions to the ribs on the members for locationtherewith, the intermediate segments positionable around the innersegments and having formations on an inner surface thereof complementaryto formations on the outer surface of the inner segments to providemechanical interlock therebetween to maintain the same in position, andan outer sleeve which passes over the intermediate segments andmechanically engages the segments and members in the end to endrelationship.

[0024] In a yet further aspect of the present invention there isprovided a method of forming the fixture components and assembling thefixture components in use.

[0025] Specific embodiments of the invention are now described withreference to the accompanying drawings; wherein

[0026]FIG. 1 illustrates a rebar in a conventional form;

[0027]FIG. 2 illustrates an inner segment in one embodiment of theinvention;

[0028]FIG. 3 illustrates two of said inner segments;

[0029]FIG. 4 illustrates the inner segments in relation to the rebar;

[0030]FIG. 5 illustrates the inner segments in position at one end ofthe rebar;

[0031]FIG. 6 illustrates the set of four inner segments, two at the endsof the two rebars to be joined together;

[0032]FIG. 7 illustrates an intermediate segment in accordance with theinvention;

[0033]FIG. 8 illustrates the intermediate segments in relation to theinner segments and rebars;

[0034]FIG. 9 illustrates the intermediate segments in position;

[0035]FIG. 10 illustrates an outer sleeve in accordance with oneembodiment of the invention;

[0036]FIG. 11 illustrates the sleeve being moved onto the intermediatesegments along the rebar;

[0037]FIG. 12 illustrates the completed fixture in accordance with oneembodiment of the invention; and

[0038]FIGS. 13a and b illustrate embodiments of tools for use with thefixture.

[0039] The requirements of the invention will be described withreference to concrete reinforcing steel bars. FIG. 1 illustrates anexample of a conventional reinforcing steel bar (rebar) 2.

[0040] The rebar 2 is available internationally in a range of sizes from6 mm to 57 mm in diameter and is provided with a series of ribs 4 on anouter surface thereof. The purpose of the ribs is to provide amechanical interface with the concrete surrounding of the bar in orderto reinforce the concrete. The ribs 4 are positioned on the outersurface in the form of a helix on two opposing sides of the bar, theribs being formed during manufacturing of said bar. The angle of thehelix on one side of the bar is typically the opposite of the angle onthe other side, to prevent “unscrewing” of the bar from the concrete.The ribs can be provided in a number of different shapes and geometriesdepending on the standard laid down in the different countries and thestructure in which the rebar is to be used.

[0041] A problem with conventional rebars is that conventionalmechanical joining methods cannot be readily applied to the same. Amethod currently employed is to deform and/or thread the end portion ofthe rebar but this typically compromises the fatigue performance of therebar and is therefore undesirable.

[0042] In accordance with the present invention mechanical joining ofthe rebar is achieved by using semi-circular inner segments 6, 8, asshown in FIGS. 2-6. The inner segments are supplied in pairs, one innersegment for each side of the rebar, and each inner segment engages withthe ribs 4 on one or other side of the bar 2. The segment pair arepre-formed before supply with an inner surface 12, 14 profiled tocorrespond closely with the rib pattern on each side of the rebar.

[0043] The engagement of the inner segments with the rebar in thismanner is a most favourable method with regard to the fatigueperformance of the rebar. This is because the inner segments do notinterrupt the surface or introduce any notches in the rebar, both ofwhich can result in fatigue crack initiation points and a common problemwith devices of this kind.

[0044] A further advantage of the joining method according to theinvention is that the correct angular alignment and co-axiality of thepair of joined bars is assured. This feature is important as failure infatigue is commonly caused by angular and/or axial misalignment, whichsets up an additional, localised bending stress as the connectionstraightens under load.

[0045] The inner segments 6, 8 can be manufactured using a typicalexample of the rebar to which the segments are to be joined as apattern. The results is that when a segment pair are subsequently fittedto a bar for splicing, their outer surfaces form a circle in section,albeit broken in two places. For example, the inner segments can be madeusing three-dimensional digitised optical scanning of the rebar. Theimage of the rebar is then inverted, manipulated and modified to providethe necessary clearance between the rebar and the segments and toproduce the dimensions for the inner segments. A thin extrudable coatingcan be applied between the rebar and inner segments to reduce anyclearance between the same.

[0046] The outer surface of the inner segments can also be profiled 16such that they provide a mechanical interlock with a similarly profiledinner surface of a further mating component, referred to herein as anintermediate segment. The profile 16 may take the form of a fine pitchthread, as shown in FIG. 3. However, it is noted that the profile couldalso be of some other form, such as parallel grooves or knurled surface.

[0047] The material chosen for the inner segments, which may becomposite in nature, will be such that some embedment and deformationtakes place on final assembly, to provide a best possible interfacebetween the rebar and the inner segments. However, the material must beable to withstand the full tensile/compressive capability of the rebarwithout movement or slip. A relatively soft material can be chosenbecause the inner segment length required to engage with sufficient ribs4 to generate enough rib shear area will always be greater than thelength required to generate enough shear area between the inner segmentand an intermediate segment This is because the substantial gaps betweenthe ribs 4 is additive to the shear area for the inner segment. Theprimary consideration is for the inner segment to engage with onlysufficient ribs on the rebar to prevent the ribs being sheared off underload.

[0048] Since the inner segments will have been manufactured using atypical example of the rebar they are to be joined therewith as apattern, the available contact area at the rib/inner segment interfacewill have been maximised thereby minimising the rib engagement lengthrequired to achieve the full tensile/compressive capability of therebar.

[0049] In practice, during assembly of the inner segments with therebar, a pair of segments will be positioned around the end of a rebaron the correct sides such that they are as near to the bar end aspossible without overhanging, as shown in FIGS. 4 & 5. The innersegments can be held in place by a spring clip (not shown), which isfitted into an undercut groove 18 provided during manufacture andlocated midway along the length of each inner segment. As there may besome longitudinal differential between the rib placements on theopposing sides of the rebar, it may be necessary to axially displace oneinner segment relative to the other. As such, the undercut groove 18 iswide enough to still contain the spring clip and allow for axialdisplacement of the segments of up to ½ of a rib pitch.

[0050] Any other resilient means can be used to secure the innersegments such as a rubber band, tying wire and/or the like.

[0051] In order to effect joining of two rebar ends 2, 2′, both rebarsare fitted with a pair of segments 6, 8, 6′, 8′, and brought togetherend to end, as shown in FIG. 6.

[0052] The inner segments 6, 8, 6′, 8′ can then be connected by afurther pair of semi-circular intermediate segments 20, 22, as shown inFIGS. 7 and 8. It is noted that more than two intermediate segments canbe used in any given assembly.

[0053] The intermediate segments 20, 22 are supplied in matching setsand are the main load-bearing component of the assembly. As such, theintermediate segments will be made from a relatively high strengthmaterial in order that their size can be minimised. The inner surfacesof the segments 20,22 are profiled 24 to correspond with the similarlyprofiled 16 outer surfaces of the inner segments, thereby providing amechanical interlock. The profile 24 can take the form of a fine pitchthread but could also be of some other form.

[0054] The cross-sectional area of the centre of the pair ofintermediate segments is preferably sufficient to be able to withstandthe full tensile capability of the rebar. The length of the intermediatesegments is preferably sufficient to encompass both pairs of innersegments 6, 8, 6′, 8′ plus the amount required for maximum pitchdifferential of each pair of inner segments.

[0055] During manufacture, the split line separating the intermediatesegments is kept to an absolute minimum. This operation can be carriedout using high pressure water jetting or other high-speed precisioncutting methods. Alternatively the inner and intermediate segments canbe manufactured using a hot stamping process.

[0056] The outer diameter of the intermediate segments has a veryshallow taper angle, in the order of, though not exclusively, one or twodegrees, the mean diameter of which lies at the centre of the component.The selection of a shallow angle to provide a frustoconical shape,referred to as coning, maximises the translated radial compressiveforce, which is applied to the inner segments and the rebar, on finalassembly. This is necessary in order to achieve the necessary embedmentrequired to minimise slip under load. A further reason for using coningis that the maximum outside diameter is dictated by the amount that thediameter at the large end of the taper is greater than the mean diameterat the centre. The use of a shallow angle minimises this. This isadvantageous as it minimises the overall profile of the finishedassembly. This is desirable because there is a requirement within theconstruction industry to maintain a minimum amount of covering concretebetween the furthest extremity of an assembled joint and the externalsurface of the concrete. The outside surfaces of the intermediatesegments may be coated with a dry lubricant layer.

[0057] In practice, during assembly, a set of intermediate segments isoffered around the pre-fitted inner segments on the pair of bars to bejoined and then brought together around the inner segments such thatthey encompass them, as shown in FIGS. 8 & 9. The intermediate segments,when brought together have an outer shape of a truncated cone.

[0058] The final component in the assembly is known as the outer sleeve26, as shown in FIG. 10. The outer sleeve has a tapered bore, the angleof which corresponds with the taper angle of the outside diameter of theintermediate segments.

[0059] The outside diameter and material choice is such that the sleeve26 deforms sufficiently to take up the shape of the irregular conedescribed by the intermediate segments, in their final positions withoutbursting.

[0060] In order to effect the connection it is driven over the set ofintermediate segments with a series of hammer blows.

[0061] The outer sleeve 26 serves two purposes. Firstly, as a result ofthe hammer blows the sleeve provides the means to generate enough radialcompressive force between the rebar and the intermediate segments toembed the inner segments both onto the rebar and into the intermediatesegments. This removes any clearances through manufacturing tolerances,which may be present, thus achieving the necessary intimacy, Secondlythe sleeve maintains the other components together in a completedassembly.

[0062] An advantage of the outer sleeve is that it requires no technicalskill in order to fit the same.

[0063] The length of the outer sleeve 26 is sufficient to encompass thelength of the intermediate segments plus an amount to allow for radialembedment of the inner and intermediate segments.

[0064] In practice, during assembly, as illustrated in FIGS. 11 & 12,the outer sleeve is installed onto the most suitable bar prior to theplacement of the intermediate segments. The large end of the outersleeve bore faces towards the joint The intermediate segments are placedwith their narrow ends towards the outer sleeve.

[0065] The intermediate segments are held in place by hand while theouter sleeve is manually pushed on as far as possible. The outer sleeveis then driven to its final position by the application of hammer blowsto the driven end as indicated by arrow 32.

[0066] The hammer 28 can be a special slide hammer as shown in FIG. 13a,or can take the conventional form, either used by itself ox with aspecially shaped “drift” 29, as shown in FIG. 13b, designed to fitsnugly around the driven end of the outer sleeve. Ideally it will takethe form of a slide hammer, being a weighted, tubular device which isopen along one side, i.e., “C” shaped in section. It will typically havea replaceable internal “C” shaped bush made of a material with a lowco-efficient of friction. It will be of sufficient length to allow it toslide freely over the ribs 4 without rocking. It will ideally be fittedwith handles.

[0067] An indication device 30 can be provided on the outer sleeve 26which acts to inform the installer when sufficient hammer blows havebeen applied. For example, a brittle ring of resinous or ceramicmaterial can be applied to the outside of the outer sleeve, which cracksand fall off when sufficient deformation of the outer sleeve hasoccurred. Another possibility is the inclusion of an undercut groove inthe region of the driven ends which will close up when sufficient hammerblows have been applied

[0068] In a further embodiment the intermediate segments can be providedwith means to clamp the inner segments and rebar together without usingthe outer sleeve. In this embodiment the requirement for theintermediate segments to be coned is removed, thereby reducing the costof the process. The means can include inner flanges which are clampedtogether by bolts. The bolts can be shear bolts. Alternatively the meanscan include a strap which can be wrapped around the intermediatesegments and tightened using a ratchet or key type mechanism.

[0069] The inner segments and or other components can be made fromeither metallic or non-metallic material. The profiles on the innersegments, and intermediate segments are typically produced by hotforging/die stamping during manufacture.

[0070] The present invention is not just restricted to the applicationof rebars but can also be used in rock anchors where a single member isjoined with an anchor using the fixture of the present invention, forjoining of any other profiled bars or for any purpose where it isnecessary to gain sufficient purchase on materials of this nature inorder to apply a load in the axial direction of the elongate member.

[0071] Thus the fixture of the present invention provides a highperformance, cost effective, mechanical connector which meets allinternational standards and requires no special equipment for barpreparation and installation.

1. A fixture for connecting two or more concrete reinforcing memberstogether in end to end relationship, said two or more members havingouter profiled surfaces, said fixture including sets of inner segments,intermediate segments and an outer sleeve and characterised in that eachset of inner segments have formations to engage with the outer profiledsurfaces of each end of the members being connected, said inner segmentformations being of complementary dimensions to the outer profiledsurfaces of the members for location therewith, the intermediatesegments having formations on an inner surface thereof complementary toformations on the outer surface of the inner segments to providemechanical interlock therebetween, and an outer sleeve positionablearound the sets of inner segments and intermediate segments to maintainthe same in position.
 2. A fixture according to claim 1 wherein the setof inner segments includes a pair of segments for location around eachend of the two ox more members.
 3. A fixture according to claim 1wherein the set of intermediate segments includes a pair of segments forlocation around said inner segments and said two or more members.
 4. Afixture according to claim 1 wherein the formations on the outer surfaceof the inner segments and the formations of the intermediate segmentsinclude any of a thread, parallel grooves or knurled surface.
 5. Afixture according to claim 1 wherein the length of the intermediatesegments or outer sleeve is sufficient to encompass at least the set ofinner segments on each member.
 6. A fixture according to claim 1 whereina semi-compressible fluid or coating is provided between the members andthe inner segments.
 7. A fixture according to claim 1 wherein the innersegments are held in place on the members using securing means, thesecuring means being located in part or whole in at least one recessportion on the outer surface of the inner segment.
 8. A fixtureaccording to claim 7 wherein the securing means includes resilientsecuring means.
 9. A fixture according to claim 1 wherein theintermediate segments are provided with fastening means to fasten thesame to the inner segments.
 10. A fixture according to claim 1 whereinthe intermediate segments forma in external frustoconical surface andthe outer sleeve has a complementary formed inner surface or bore toallow a locking action to be exerted on the intermediate segments.
 11. Afixture according to claim 1 wherein the outer sleeve is provided withan indication device on an outer surface thereof.
 12. A fixtureaccording to claim 1 wherein the two or members are elongate bars andthe outer profiled surface of the members comprises a plurality of ribs.13. A fixture for connecting at least one concrete reinforcing member toan object, said at least one member having outer profiled surfaces, saidfixture including sets of inner segments, intermediate segments and anouter sleeve and characterised in that each set of inner segments haveformations to engage with the outer profiled surfaces of each end of themembers being connected, said inner segment formations being ofcomplementary dimensions to the outer profiled surfaces of the membersfor location therewith, the intermediate segments having formations onan inner surface thereof complementary to formations on the outersurface of the inner segments to provide mechanical interlocktherebetween, and an outer sleeve positionable around the sets of innersegments and intermediate segments to maintain the same in position. 14.A fixture according to claim 13 wherein the object is an anchor.
 15. Afixture fox connecting two or more elongate concrete reinforcing membersin end to end relationship, said members provided with ribs on anexternal surface thereof, said fixture including sets of inner segments,intermediate segments and an outer sleeve and characterised in that eachset of inner segments have formations to engage with the ribs at eachend of the members being connected, said inner segment formations beingof complementary dimensions to the ribs on the members for locationtherewith, the intermediate segments positionable around the innersegments and having formations on an inner surface thereof complementaryto formations on the outer surface of the inner segments to providemechanical interlock therebetween to maintain the same in position, andan outer sleeve which passes over the intermediate segments andmechanically engages the segments and members in the end to endrelationship.
 16. A method of manufacturing a fixture according to claim1 wherein the inner segments are formed by three dimensional digitisedoptical scanning of examples of the members to be joined to form animage, inverting the image obtained and modifying the dimensions of theimage sufficiently to allow the inner segments to be placed around themembers for engagement, said inner segments formed with a surface inaccordance with the image obtained from the scanning process.
 17. Amethod of manufacturing a fixture according to claim 1 wherein a splitline of the intermediate segments is formed using any or any combinationof high pressure water jetting or hot forging.
 18. A method of using afixture according to claim 1 wherein a set of inner segments are placedaround two members at the ends thereof which are to be joined end toend, and as near to the end of the member as possible withoutoverhanging said end, and a set of intermediate segments encompass thetwo members and the inner segments.
 19. A method of using a fixtureaccording to claim 1 wherein the outer sleeve is installed over a memberprior to the placement of intermediate segments, a larger end of theouter sleeve bore facing towards the join between the two members beingconnected, locating intermediate segments over the inner segments on themembers with narrow ends of the intermediate segments facing the outersleeve, and then hammering the outer sleeve over the intermediatesegment.